It's armour parts flying 800 miles in a minute (with no apparent power source), but when forming a complete armour (and now powered by Tony's arc reactor), that armour can't fly.

It's flying armour parts not being able to break through a wooden door, but breaking through everything else.

It's an attack with three helicopters on the house of a billionaire who has several battle armours there, each armour capable of taking out 25 helicopters - and the attack succeeds because the genius billionaire is too stupid to have a simple radar-based defense system after challenging the world's top terrorist.